The invention relates to a dental transfer element.
EP-A-0 727 193 discloses such a transfer element the guide sleeve of which can be connected by means of a core to the implant body previously implanted in the jaw bone. In the area of its coronal end, the implant body has a recess with guide faces aligned axially in parallel in the manner of a hexagon for anti-rotational blocking of a construct that can be connected to the implant body to which a superstructure, a crown or the like, can be fixed. When implant-supported superstructures, crown constructs or the like are created using a master model, a precise transfer of the axial as well as the circular implant position is very important. Corresponding to the hexagonal guide faces, the core is therefore also provided with hexagonally arranged positioning elements formed as outer surfaces aligned in parallel at the end of the core, which engage with the implant body. In other respects the core is essentially arranged within the guide sleeve, which in its area facing the coronal end of the implant body has further positioning elements corresponding to the positioning elements of the core. These further positioning elements are formed as interior hexagonal surfaces. Production of the further positioning elements of the guide sleeve formed as interior surfaces is quite costly. Very close tolerances must be met to permit the transfer of the angular position of rotation of the implant body to a master model by means of the guide sleeve and the impression material. Even slight differences or gaps between the hexagonal interior surface of the guide sleeve and the hexagonal outer surface of the core, which would normally be within tolerance, lead to a significant deviation in the rotational position of the guide sleeve. Despite high-precision production of the interior hexagonal surfaces of the positioning elements of the guide sleeve, transfer errors of the angular position of rotation are difficult to avoid in practice.
WO-A 93/20774 discloses such a transfer element whose core also has positioning elements in the form of hexagonal surfaces, which engage with a hexagon of the implant body. The core, which is capable of axial displacement within the guide sleeve, comprises an axially parallel flattened area, which fits against an axially parallel flattened interior surface of the guide sleeve. In other respects the outer surfaces of the core and the interior surfaces of the guide sleeve fitting against them are cylindrical. In this embodiment, too, the production of said flattened interior surfaces of the guide sleeve is quite costly and even slight deviations due to manufacturing tolerances cause a considerable angle error in the transfer of the angular position.
U.S. Pat. No. 4,758,161 discloses an insert element, which may be connected with the implant body. The insert element comprises a shaft, which may be inserted into an axial recess of the implant body and anchored therein, particularly with dental cement. The insert element further comprises a head for fastening a crown or superstructure. Said head has radial grooves, a constriction and a flattened area for defined localization of the crown or superstructure.
Based thereon, it is the object of the invention to ensure a simple impression procedure while nevertheless obtaining great precision in the transfer of the angular position. The handling in the dental practice and in the laboratory is also to be improved.
This object is attained by the invention as described and claimed hereinafter.
The transfer element according to the invention is distinguished by its functional construction, serves as a repositioning aid, and ensures with great precision the molding and transfer of the implant position in axial, radial and circumferential direction. The transfer element has two parts comprising on the one hand a core and on the other hand a guide sleeve with mutually corresponding positioning elements for a reciprocal positive-locking, defined fixation in circumferential as well as axial direction. The core is hollow on the inside so that a retaining screw can be guided through it, and it can be axially inserted into the sleeve. The positioning elements, which are advantageously formed as a radial projection and a radial recess, respectively, readily assure an exact mutual alignment. The core has a simple contour and/or geometry and is not costly to produce. The core is partly cylindrical and may be pushed into the sleeve. To take the impression, particularly with an open scoop, the core and the sleeve can be fixed to the implant body implanted into the jaw by means of the retaining screw. When the impression is taken with the open scoop, which is perforated in the implant region, the head of a correspondingly long retaining screw is guided through the perforation. After the scoop is removed, the transfer element remains in the impression and does not need to be repositioned. The core at its one end is advantageously provided with the positioning element and at its diametrically opposite end with the anti-rotational blocking element, particularly in the form of a hexagon, which may be engaged with a corresponding anti-rotational blocking element in the implant body.
The transfer of the circular and axial implant position to the master model by means of the transfer element is thus ensured, and a significantly improved overall accuracy of fit of the superstructure is achieved. The sleeve according to the invention extends up to the gum region and the axial end face fits directly against the axial front face of the implant body, with the end face and front face having substantially the same outside diameter. The axial length of the guide sleeve is at least 50%, particularly at least 65% of the axial core length. On its outer surface the sleeve has at least one constriction, recess, retention element or the like to ensure exact positioning in the impression material. The retention elements to secure the rotational position and/or the axial position in the impression material can advantageously be in the form of flattened areas arranged on the outer surface and produced particularly by milling, or in the form of longitudinal grooves or blind holes or the like. The constriction or recess is advantageously provided approximately in the center of the axial longitudinal extension of the sleeve. The part facing away from the implant body has a substantially cylindrical or approximately conical outer contour, the tip of which is also located on the side facing away from the implant body. The part of the sleeve facing toward the implant body has an outer contour corresponding to the dental construct element in the passage area of the gums and/or the corresponding gum former.
Further developments and specific embodiments of the invention are set forth in the following description.